This invention relates to noninvasive testing of the internal conditions of fluid-filled containers such as pipes, cylinders, etc., and to novel ultrasound methods for testing these internal conditions.
Pursuant to 37 C.F.R. 1.71 (e), Applicants note that a portion of this disclosure contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
Detecting inner wall corrosion in containers such as pipes, conduits, cylinders, tanks, pressure vessels, etc. has been a longstanding concern in many industries. For example, MIC (microbiologically influenced corrosion) in water systems is of particular concern. Microbes live in water everywhere and are difficult to kill. Corrosion pitting, slimy fluid and rusty nodules are often the products of MIC. Such corrosion and foreign objects cause wall thinning and reduction of flow area that are detrimental to the structural performance of pipes or other containers, and can sometimes lead to disastrous consequences. Chemical, petroleum, water utility, fire and power industries have been battling MIC and other forms of internal container (e.g., pipe) corrosion (e.g., in water and other fluid storage and/or conducting systems) for many years.
Many nondestructive or noninvasive methods have been applied, with varying degrees of success, to locating MIC and assessing its effects. X-ray and gamma ray radiographs provide images that can be used to gauge the presence of MIC, the amount of occlusion and wall thinning. However, drawbacks of these methods include slow inspection speed, high cost and safety/health concern issues.
Ultrasonic thickness gauging is used routinely to measure wall thickness in refinery piping and tanks. Compared to radiography, ultrasound is cheaper and doesn""t emit harmful radiation. A single thickness gauge measurement is much faster than radiography, but it only covers a localized area the size of the transducer used in the measurement. Thus, to obtain the thickness information over a large area, the ultrasonic thickness gauge method may not be as fast as radiographic methods. More importantly, a wall thickness reading at a given point depends on good through-thickness echoes so that an accurate time can be measured. Rough corroded internal wall surface and porous MIC nodules make it difficult to get a valid reading. Often the wall thickness reading is greater than nominal. In some cases, no echoes are available because the ultrasonic energy is simply absorbed or scattered. The ultrasonic thickness gauge is not used to detect the existence of, e.g., slimy fluid either.
The present invention overcomes these and other limitations of the prior art by providing new methods, apparatus and integrated systems for measuring features of fluid filled containers (e.g., pipes, tanks, barrels, drums, cylinders, plates and other structures) and a variety of other features that will become apparent upon complete review of the following.
A xe2x80x9cleaky guided wave ultrasoundxe2x80x9d (LGWU) method is provided for fast and reliable detection of features on the internal walls of containers (e.g., pipes, conduits, tanks, barrels, drums, cylinders, plates and other appropriate structures that will be apparent upon further review of the following), such as container wall irregularities, loss of wall material, pitting, corrosion, MIC, or the like, as well as for the detection of foreign objects, e.g., in fluid-filled containers. Material in the pipes, whether deliberate (e.g., container structural features) or unintended (e.g., ice or foreign objects) can also be detected.
The methods, devices and systems herein are generally applicable to structures and systems that can be configured to comprise one or more gas, solid or fluid. The methods, systems and devices herein are particularly well-suited to structures and systems comprising fluid filled containers.
In the methods of the invention, a transmitting transducer (e.g., placed circumferentially on the outside of the container) excites a guided wave, and part of its energy leaks into a material such as a fluid in a container. The leaking wave travels through the fluid or other material, reflects off the container inner wall and enters the receiving transducer.
The LGWU method measures both the direct field, and the leakage field inside the fluid generated by the guided ultrasonic waves. Since the leakage field interacts directly and, typically, only, with the fluid and inner container wall, the LGWU method is able to reliably detect corrosion, MIC and other features on container inner walls (e.g., the insides of pipes), as well as fluid level and composition, including foreign objects inside the fluid.
By calibrating against the measured direct field, the LGWU method is not sensitive to the container outside wall surface condition, such as the existence of paint, rust or dust. In addition, a single LGWU measurement covers a significant portion of the circumference of the container. Therefore, as few as two or three LGWU measurement locations can provide approximately 100% inspection coverage of an entire container circumference. Thus, the inspection speed is faster than any prior methods. The LGWU method can also be used to accurately detect fluid level (e.g., whether water, hydrocarbon or other fluid type) in the container, or the existence of ice in the container, e.g., due to frozen condensation water.
The present invention also provides devices, apparatus, integrated systems and kits for practicing the methods of the invention. For example, the invention provides an integrated system and/or device for detecting corrosion and MIC on the inner wall of fluid-filled containers such as pipes, foreign objects in the fluid, and/or fluid level using leaky guided wave ultrasound (LGWU).
The system/device includes components for performing the method above, such as a transmitting transducer and a receiving transducer or a single pulse-echo transducer configured for placement at circumferential or longitudinal positions of a fluid-filled container, a wave generator or pulser which produces a shaped tone burst pulse at a specified frequency or uses a resonant transducer excited by a spike or rectangular pulse to create the specified frequency and detection modules consisting of a receiving transducer or transducers connected to both digital and analog amplifiers and filters, analog to digital converters controlled by software or firmware and digital electronic storage media for the purpose of measuring both a direct field and a leakage field, software and/or firmware for analyzing the direct and leakage field signals, thereby providing an indication of existence of corrosion and MIC on the container inner wall, foreign objects inside the fluid and fluid level.
The guided wave can be excited at a selected frequency and angle to maximize the leakage field for selected container ODs and materials. Other suitable wave characteristics can also be selected or modulated in the methods and systems herein; e.g., the amplitude of a given phase point on the tone bursts can be modulated or selected.
The device, apparatus, kit or system can include a computer or computer readable medium having an instruction set for controlling the system e.g., for controlling the transmitting transducer the guided wave generator, or the like. The computer or computer readable medium (or multiple associated computers or computer media) can include other relevant instruction sets, e.g., for measuring the direct field and the leakage field, reporting the results of the measurement to a user, running a graphical display of the relevant results, or the like. Kits can include any of the apparatus or integrated systems elements plus containers for storing the apparatus or system elements, instructions in using the apparatus or integrated systems elements, e.g., to practice the methods herein, packaging, etc.
A presently preferred method/system is to use an arbitrary function generator (which, e.g., generates a pulse at a user-defined frequency) in combination with a wideband transducer, so that a range of frequencies can be excited and received. This approach typically uses computer software to control and shape the pulse and frequency along with wideband amplifiers and filters. The system device includes the geometrical configurations and various media that can be used to couple the transducers to the container, tank or structure.
Further objects and advantages of the invention will become apparent from a consideration of the drawings and description.